1. Field of the Invention
The invention relates to a secondary battery housing and control electronics.
2. The Prior Art
High capacity secondary batteries are formed by packing multiple rechargeable cells into a housing. The packing configuration can occupy a large volume, inadequately protect the cells from impact shock or lead to overheating. In addition, the battery requires sophisticated electronics to balance the charge between high and low voltage cells, protect the system from over-voltage conditions, efficiently convert power for output, provide suitable smart connectors, and provide battery status indicators.
A prior art example of a battery module is disclosed in U.S. Pat. No. 8,530,069 where cylindrical cells are packed into an upper tray and a differently configured lower tray. The cells are retained in sockets with bus bars coupling the cells together at the top end only. Posts 54 raise the lower tray to create a vent chamber. Wires extend out of the housing to external sensors. The prior art patent does not isolate battery packs from each other nor does it provide control electronics within the housing.
Batteries for these specialized applications having multiple cells require cell balance converters. Most cell balance converters are either passive or utilize “hard switching topology.” The passive devices dissipate power leading to inefficiency. The converters based on “hard switching topology” produce a large amount of EMI. Furthermore, all commercially available converters suffer from consuming more than 120 mW, design limitations preventing operation at 33V, or no isolation. One prior art cell balance converter is disclosed in U.S. Pat. No. 9,172,257. The converter circuit has a complex secondary winding configuration and does not provide a capacitor in the series loop with the battery and the winding. U.S. Pat. No. 9,142,979 shows an alternate configuration, however the circuit lacks a capacitor on the battery/switch series loop.
When incorporating a battery protection switch, a low power isolated converter is needed which can operate throughout the varying battery terminal voltage range. Certain solutions have been proposed in U.S. Pat. No. 6,370,050 and U.S. Published Patent Application 2009/0206657. However, both references use multiple switches on each battery loop which adds to the cost, power usage and complexity of the control circuit. Other examples in non-battery applications can be found in U.S. Pat. No. 5,325,283 and U.S. Pat. No. 4,959,764 and U.S. Pat. No. 6,069,803 and U.S. Pat. No. 8,749,995. Since these circuits draw from mains power, conserving space and low power consumption are not addressed.
When multiple cells are present it is desirable to provide a corresponding number of bidirectional switches that allow individual control of the charge and discharge paths. In addition the switch paths require balancing resistors and bypass capacitors. Normally, bilateral semiconductor switches are not used at this current level integrated with the bus bar inside a battery. U.S. Pat. No. 7,193,392 provides multiple switch paths but does not have the switch integrated with the bus. U.S. Pat. No. 9,054,400 has the semiconductor switch attached to the bus, but does not disclose bidirectional switches with individual paths.
Presently battery electronic switches are opened slowly so not to produce large transients or they use contactors which are not prone to damage by voltage transients.
Current 6T batteries are non-smart batteries, having limitations with regard to interconnecting of batteries and display of State of Charge, Voltage, Current and other pertinent battery information.
Currently thermal protection is achieved by low cost encapsulated thermistors which are subject to electromagnetic radiation that can affect the validity of the temperature measurements.